Process for preparing vaccine adjuvant

In a process for preparing a water-soluble immunological non-specific adjuvant for enhancing the effect of vaccine, the improvement which comprises

• treating with a murolytic enzyme, in an aqueous solution, a suspension of Mycobacteria or Nocardia cells walls, said cell walls being substantially free of waxes, free lipids, free proteins and of nucleic acids,
• separating the solid residue including cell walls residue from the digested residue and,
• recovering the aqueous portion containing water-soluble immunological adjuvant, the adjuvant having reduced sensitizing action to tuberculin.